When an oil spill occurs, the most desirable remedy is recovery of the spilled oil. However, rarely is more than 10% of the oil released in a major spill ultimately recovered. Oil that cannot be recovered may be dispersed, thus protecting shorelines, preventing the oiling of marine birds and mammals, and speeding oil biodegradation. Oil dispersal has not been universally satisfactory, however, mainly due to the high toxicity of currently available dispersants.
Many dispersants are surfactant-based. However, there is reason to believe that the efficacy of such dispersants is directly correlated with their toxicity. A surfactant at a concentration sufficient to emulsify petroleum may also be expected to have deleterious effects on marine organisms. Such effects include tissue irritation, changes in gill membrane permeability that promote asphyxiation and an increase in the uptake of chemical pollutants.
Commercially available oil dispersants are all liquids and possess relatively low LD.sub.50 s (high toxicity). These include COREXIT.RTM. 9527 (Exxon), a surfactant-solvent product for oil dispersal; NAXCHEM.RTM. Dispersant K (formerly known as Conco Dispersant K and now sold by Ruetgers-Nease), a product consisting primarily of surfactants and alcohols; ATLANT'OL.RTM. AT-7 (Aspra, Inc.), a water-based product; OMNI-CLEAN.RTM. OSD (Delta Omega Technologies), a water-based product containing synthetic surfactants and fatty acid soaps and marketed as a safe, low-toxicity product; COREXIT.RTM. 9550 (Exxon); and COREXIT.RTM. 7664 (Exxon), a product formerly marketed as an open-sea dispersant but now sold mostly as a beach cleaner.
Surfactants added to oil slicks on water tend to be immediately diluted by the water. Only when sufficient surfactant concentration is in contact with both water and oil will dispersal occur. Once the surfactant has solubilized the oil, the dispersed droplets mix with greater and greater quantities of water. While this is the desired effect of dispersal, it also tends to further dilute the surfactant concentration, so that resurfacing of oil slicks may occur.
Related U.S. application Ser. No. 08/027,861, now U.S. Pat. No. 5,399,350, discloses the use of a substantially intact proteinaceous particulate material derived from grains as an oil emulsifier and high efficiency dispersant. Exemplified materials typically have been milled, solvent extracted, and separated from other components of grains. While this material has excellent dispersal properties, it is somewhat expensive for widespread use. Moreover, it is produced by an exacting process that requires careful process control and dedicated production equipment. As a result, the worldwide production capacity is currently insufficient to permit large scale use on major oil spills.
Thus, there is a need for a lower cost, readily available, natural non-toxic material useful as an oil dispersant that is available in large quantities. The present invention provides such a material and a method for using it in remediation of environmental spills.